1. Field of the Invention
The invention relates to a catheter wire and, in particular, to a catheter wire that is to be equipped with an ultrasonic transducer and is good in a straight-advancing property and electrical characteristics in a bent state while a diameter thereof is reduced.
2. Description of the Related Art
As shown in FIG. 2, a conventional catheter wire is formed by twisting plural (seven in the illustrated example) enamel wires 100 in each of which a copper-alloy wire 110 is covered with a coating layer 120 formed of polyimide.
Meanwhile, a twisted wire 200 as shown in FIG. 3 is also known, in which a signal wire 210A and a ground wire 210B as a pair of insulated wires 210 each formed by covering a copper alloy twisted wire with an insulation are wound around an outer periphery of a central conductor wire 220 at a predetermined pitch.
Furthermore, a multicore cable 300 as shown in FIG. 4 is also known, in which coaxial cables 340 are twisted together around an outer periphery of a tension member 350 to form a core bundle, a binding tape 360 is wound around the core bundle and a shield layer 370 and a sheath 380 are further provided thereon. Each coaxial cable 340 is composed of an extra-fine insulated wire 310 formed by covering an inner conductor with an insulation, a conductor wire 320 wound therearound and a jacket layer 330 covering the conductor wire 320.
Such a catheter wire is disclosed in, e.g., U.S. Pat. No. 8,143,517.